NETWORKS(5) Standards, Environments, and Macros NETWORKS(5)


networks - network name database





The networks file is a local source of information regarding the networks
which comprise the Internet. The networks file can be used in conjunction
with, or instead of, other networks sources, including the NIS maps
networks.byname and networks.byaddr. Programs use the
getnetbyname(3SOCKET) routines to access this information.

The network file has a single line for each network, with the following

official-network-name network-number aliases

Items are separated by any number of SPACE or TAB characters. A `#'
indicates the beginning of a comment. Characters up to the end of the
line are not interpreted by routines which search the file. This file is
normally created from the official network database maintained at the
Network Information Control Center (NIC), though local changes may be
required to bring it up to date regarding unofficial aliases and/or
unknown networks.

Network numbers may be specified in the conventional dot (`.') notation
using the inet_network routine from the Internet address manipulation
library, inet(4P). Network names may contain any printable character
other than a field delimiter, NEWLINE, or comment character.


getnetbyaddr(3SOCKET), getnetbyname(3SOCKET), inet(3SOCKET), inet(4P),


The official SVR4 name of the networks file is /etc/inet/networks. The
symbolic link /etc/networks exists for BSD compatibility.

The network number in networks database is the host address shifted to
the right by the number of 0 bits in the address mask. For example, for
the address that has a mask of fffffe00, its network number
is 803351. This is obtained when the address is shifted right by 9 bits.
The address maps to 12.66.23. The trailing 0 bits should not be
specified. The network number here is different from that described in
netmasks(5). For this example, the entry in netmasks would be

February 25, 2017 NETWORKS(5)